Nmr Detection of Intramolecular Oh/oh Hydrogen Bond Networks: an Approach Using Isotopic Perturbation and Hydrogen Bond Mediated Ohoh J-coupling

A series of conformationally restricted triol and tetrol systems containing intramolecular hydrogen bond arrays has been prepared and characterized by X-ray crystallography and NMR spectroscopy. NMR isotopic perturbation measurements in DMSO-d6 and CD2Cl2 reveal that this methodology can be used to detect the spatial proximity of up to four contiguous hydroxyl groups sharing a 1,3-, 1,4-, or 1,5relationship. Furthermore, hydrogen bond mediated scalar couplings can be used to assign the identity of NMR resonances arising from perturbed OH signals. Our studies suggest that isotope shifts in OHOH networks are additive. An application in the area of natural product structure elucidation is presented. INTRODUCTION It is well-known from solid state studies that intraand intermolecular arrays of hydroxyl groups can form continuous and cooperative hydrogen bond networks. Intramolecular OH/OH networks also have relevance in discussions of the solution conformational behavior of carbohydrates and natural products, especially those containing polyacetate and polypropionate motifs (Figure 1). Systems with strong intramolecular OH/OH hydrogen bonds have also emerged as a promising class of functional organocatalysts. The focus of this paper is a description of new NMR methodology for detecting networks of intramolecular OH/OH hydrogen bonds for hydroxyl-containing systems in solution. HETEROCYCLES, Vol. 72, 2007 469